Fluid rotor



E. A. STALKER April 3, 1934.

FLUID ROTOR Filed July 23, 1932 8 Sheets-Sheet l g i W/V/f/k April 1934- E. A. STALKER 1,953,444

FLUID ROTOR Filed July 25, 1932 8 Sheets-Sheet 2 Mam April 1934- E. A. STALKER 1,953,444

FLUID ROTOR Filed July 23,.1932 8 Sheets-Sheet 3 8 Sheets-Sheet 4 FLUID ROTOR Filed July 23. 1932 E. A. s'rALKR April 3, 1934.

E. A. STALKER April 3, 1934.

FLUID-ROTOR Filed July 23, 1932 8 Sheets-Sheet 5 April 3, 1934. E. A. STALKER 1,953,444

FLUID ROTOR Filed July 23, 1932 8 Sheets-Sheet 6 April 3, 1934. E A. STALKER 1,953,444

FLUID ROTOR Filed July 25. 1932 8 Sheets-Sheet 7 April 3, 1934. E. A. STALKER 1,953,444

FLUID ROTOR Filed July 23, 1 932 8 Sheets-Sheet 8 w/w/m Patented Apr. 3, 1934 1,953,444 FLUID ROTOR Edward A. Stalker, Ann Arbor, Mich. Application July 23, 1932, Serial No. 624,341

20 Claims.

My invention relates to improvements in aeroelectric power plants in which the elements experiencing a cross-wind force move substantially parallel to themselves; and the objects of my improvements are, first to provide an arrangement of elements capable of extracting the maximum amount of energy from the wind; second, to provide a structural design that iseconomical and efficient; third, to provide elements of sumciently low cost that they may be combined economically to form a plant of the proportions dictated by the theory here developed; and, as shown by the theory, necessary to extract the maximum energy from the wind.

I'attain these objects by the devices illustrat ed in the accompanying drawings in which Figures 1a to 1 are diagrams related to the theory. Figure 2 shows a plan view of a power plant while Figure 3 shows the elevation. Figures 4 and 5 depict in more detailthe design of the wings and their supporting structure; Figures 6 and 7 show the means of driving the electric generator through the axle mechanism and the method of housing the generator in the wing; Figures 8, 9, 10, and 11 illustrate the method of rotating the wing to the correct angle, dependent on the direction of the wind. Figures 12 and 13 show the means to operate the wing flap. Figure 14 is a plan of the wing with parts removed to show the motor and worm tip while Figure 15 is a front view of the wing tip and end disk. Figure 16 is a section through the end disk. Figure 17 is a sectional view taken along 17-17 of Figure 15.

Similar numerals refer throughout the several views.

Proposed rotor plants rely on their weight to prevent their being turned over by the relative wind; Since the addition of weight increases the rolling friction of the car there is a very definite economical height for the rotors. This is a disadvantage since the maximum power output of a plant is proportional to the product of the height and the length of thetrack. The diameter or breadth of the plant is testricted by the area of the land available, but the height is not restricted except by the type of design. A wing is defined as a body elongated in the direction of the wind-and capable of producing a lift or cross- ..wind force, t

It is'not contemplated to make any claims dealing with the mounting of a rotor on a car travel ling over a double track with the object, of generating electricity and. placing reliance on the 7, weight .of the rotor and car to prevent overturnto similar parts ing by the wind. Rather it will belshown that another system can be constructed five timesfas effective in extracting energy from the wind and of a design that will permit extremely high strum tures to be built, and consequently plants of several times the power output of a rotor plant for the same land area. Qther advantages will appear from the development of the theory which.

where A is the area of the wing and CL and CD are the well known coeflicientsof lift and drag. Since V am (2) In general will be small enough so that tan tp sin very closely. Hence p 3 P=C AV (s) Differentiate Equation (5) with respect to 4;, and set it equal to zero to determine the value of for P to be a maximum. It is tan Y Hence 2 Pmax 27 (CD2) max pAVs It is known in aerodynamics that the drag COefilcient may be divided into a profile dragcoefficient (Cop) dependent on the air friction, and an other drag-coefficient due to the finiteness of the span (or tip loss). The latter is called the induced drag coefiicient (Cm). Then CD:CDP+ m (7) n CLQA 2i CDP+WCDP+WRH z R =equivalent aspect ratio That is, the induced drag depends on the square of the lift coefficient and the plan form of the wing. The factor k modifies the span S of the wing to account for variations. of the plan form from an ellipse. I

It may be found in the literature that One may be expressed as a function of the thickness of the C p 0.0053+0.0317i By the calculus method of determining a maximum, it follows that CD2 max 161/CDP In like manner, for maximum power output El; 37rR L W a DP Hence by substituting the value of tan 5:6

1 (7D2 max in Equation (6) /31r f fljksy 3 mnx CDPTV This is the maximum power output for one wing always entering undisturbed air moving with the velocity V relative to theearth- This equation has a geometrical interpretation. In Figure 1b construct the circle of diameter equal to the span. The volume of air passing through this circle is equivalent to the volume from which the wing extracts the energy.

As a matter of fact, theair is disturbed, by the wing, at great distance from the wing, but all these efiects may be accounted for by assuming a uniform retardation of the flow through the area This area is called the sweep of the wing. If the wing has end disks or is not elliptic in plan form, the factor 70 changes the area somewhat. In the case of rectangular wings 7c is so near unity that it may be so taken.

If there are a great many wings it may be shown that the sweep of the individual wings is wing expressed as a fraction of the chord. That where n is the number of wings of area A.

Also the factor kn, the equivalent monoplane span factor for a multiplane system is the square root of the ratio of the sweep of the system to the sweep of a simple monoplane wing. Thus if G is the gap between wings measured normal to the relative wind,

very closely if the set of n wings are a group forming a closed system. Such a closed system would be formed by the wings following a circular path.

This equation for It is also sufficiently accurate if the circular areas at the ends of the system may be neglected in comparison to the area between the wings. Such is the case here where the circuit is always closed.

The maximum. power that can be extracted from the wind by n wings is then k S) Pm...= V 16 72 /C pnA Also the equivalent area or sweep through which the relative wind passes is the product of the height S and the projection of B on a line normal to the relative wind. Thus the sweep: BS sin 4). From the geometry of Figure 1d Also from the geometry of Figure 1d, and the definition of the factor kn 4 B 2= I K 7r szn (,6 (18) Equations (17) and (18) lead back to Using Equation (19) in conjunction with Equation (16) the latter becomes A. rotor has a profile drag coefficientof about 0.25 while a wing may have a value of 0.01. Since the power is inversely proportional to.

'\/CDP the wing system can produce times as much power asa rotor system.

If the wings travel on a closed circuit, the windward arc may be thought of as projected on the diameter lying at: right angles to the wind, and the equations for P relate to this projection considered asa straight path. If the leeward arc is well downwind from the windward, the power output; on this are may be taken equal to the windward .arc; The total power output is then twice that of Equation (20). On the other hand the anglemust be measured'between the tangent to? the true path and the wind direction.

If we determine by the calculusthe value .of G1. which makes CL3/CD2 a-maximum, the value 5 of C1. for maximum power is found-Thezlift coefficient is for this condition I It is desirable to relate the lift coefficient to the angle of attack of the wing. It is best tomeasure the angle from a line in the wing such that when the relative wind blows along this line the-lift is zero. This zero lift line may be found as in Figure 1e. Through the trailing edge and the mid point of the mean camber line 01 draw the straight line marked L=0. The angle between the zero lift, line and the wind direction is the angle of attack.

The relative wind makes the angle 5 with the track and the wing makes the angle on with the relative wind. Hence the angle between the zero lift line and the track is (see Fig. lg)

The value of Cup is defined by Equation (8a).

The value 0 defines the best angle for the wings '45 relative to the track for each windcondition.

In any case of maximum power the track speed is 6, GDP 37rR To recapitulate the maximum power for a multiplicity of wings is obtained when the path speed is The maximum power is then very closely, for both sides of the circuit The" above equations define the conditions for maximum power. v

When the number of wings is specified R15 is i-g immediately determined and hence the track- ZO iner 2n (G/S) p'V 7 speed, assuming that the wing section and'plan form have been also chosen. Hence a plant of n wings per one side of the diameter taken normal to the relative wind, operates at maximum power with only one speed to wind ratio. Any other speed ratio gives less power. Also, any other angle of attack will give less power.

Since the ratio of track speed to wind speed is the tangent of qb, the variation of power output or the variation of the wind-track speed ratio is '85 statable in terms of t. To set the limits of 1 from which the claims limits for 0 may be stated return to the general Equation 5 for the power output under any conditions.

In Equation (5),

' 91 C tan (5 is a small number since a CL is small. Thus as a first approximation thepower is inversely proportional to the square of the tangent of 5. As a matter of fact, however, P will decrease less rapidly than l/tan b because of the last term. This Equation (5) determines the upper value or range of Q for the claims. The following table shows how P varies with (5 if everything else is kept constant.

Table I /01 7of 70f 01 701 01 W tan r oo P 100 PO=10O P =100 P lot e ico no It will be noted from Table I that the power output is sensitive to the angle For instance, if the structure of the plant specifies 6 as the most efiicient angle (P=100%) a change of angle to 8, maintaining everything else constant including. the track speed, the power output falls to 53.2% as indicated in column 5.

If the most eflicient angle were 8 a change to 12 would drop the power to 43.9% as shown-in column 6. A 50% increase in the angle for maximum power will cause about a 50% drop in they power output.

The most economical angles are the relatively small angles for it must be remembered that power is force times velocity. If a low track velocity is used a great many wing units must be used to obtain a given power. It .is therefore bestto use as few wing units as possible. 'Ihe 1'35 permissible maximum track speed sets the lower limitto the number of wing units. For this reason .it is not likely that tan- 9 will be much less than-0.166 for which s is 9-30-'. The preferred gap is .then of. the order of the height of the wing. but this is not to be regarded a limiting, dimension. Furthermore, improvements in presentday track cars. may make practicable much smaller values of I It'has been shown that the-maximum power is proportional'to C /C15 and that here C /31rRa c shows for a monoplane how the value of CIfi/CD varies with a. measured from the zero lift line. The wing section is National Advisory Committee for Aeronautics M-6 with a trailing edge flap at degrees. It will be observed that a 50% variation in a to either side of amax decreases the factor CL3/CD2 by about 30%.

The mechanical and structural features by which I carry the theory into practice will be clear from the drawings and the following description- In Figures 2, 3 and 4 the wings 1 are mounted on wheels 2 and travel on the track 3. The wings are interconnected by the cables 4 and 5. In the lower section of a wing is mounted an electric generator 7 (see Figure 6) which is geared to the axle of the wheels. The wind propels the wings along the track and as a result electric energy is generated.

The wings are supported, against overturning, by the structural framework 8. These frames are placed at intervals about the track and carry a continuous track 9 shown as a solid I-section in the Figure 4. In actual practice this frame may be built up of lattice structure for lightness.

The structure connecting the wings to the upright frames is shown best in Figures 4 and 5. A connecting rod 10 carries the rollers 11 and 12 at its forked end. Only one set of rollers bear on the I beam at any instant. The connecting rod has a vertical hinge connection 13 at the wing end, permitting the wing to pivot when desired. The connecting rod is sloped upward so that the frame 8 need not be tall.

The generator '7 is geared to the axles 17 of the cars by the gears l8, 19, 20, 21, 22, and 23a. (See Figures 6 and 7.)

It is sometimes undesirable to run the generator at speeds varying with the wind velocity, yet it is desirable to extract the maximum amount of energy from the wind. If the ratio of angular ve- 560! output.

- ent speed is desired the'gear 23a is disengaged from 23 and 22a is engaged with 22. of combinations may be added.

Due to the upwardinclination of the supporte ting rod 10 .there will be a tendency to lift the wing fromv its track when the wing is on one side of the track circuit. (See Figure 4.) On the Any number opposite side the tendency is to increase the pressure. of the wheels on the track. Figure-6 shows the method used to maintain good bearing of the wheels on the track under all conditions. The frame 24 of the wing carries two forked frames 25 and 26 which in turn provide bearings for the wheel axles 27 and 28. Between the end bearings of the parts 25 and 26 two links 29 and 30 extend downward to carry the wheels 31 and 32. These are also interconnected by the link 33. If the wing tends to rise from the track it is obvious that the wheels 2 are pressed more tightly against the track, and there is therefore no loss, through slippage, of driving action for the generator.

Provisions are also made to turn the wing through various angles as the wing progresses along the track so that at all times the wing gives its best effect. Along the portion of' the track more or less normal to the wind direction the angles 0 and should have values defined by Equations (28) and (31) respectively.

The angular attitude of the wing toward the track must be varied to obtain the maximum power. The rotation of the wing takes place about the vertical shaft 34a which is rigidly attached to the wing framework 34. The shaft extends downward into the generator compartment 35 which does not change its attitude with respect to the track. The disk 36 is rigidly attached to the lower compartment. Antifrlction bearings at 37 and 37a facilitate the rotation of the wing which is accomplished by the motor 38 through the worm 39 and gear 40.

The angular attitude of the wings on various segments of the track may be made to depend on the wind direction and intensity. In Figure 8 the wind vane 41 is located far enough away from the wings to be undisturbed by them and so registers the true direction. The vane may also be located near the wings and a correction made for interference. The vane is rigidly connected to the housing 42 which is free to turn on ball bearings at its base. The housing supports a number of self-synchronous motors 43 sold in the case of the General Electric Company under the trade name of Selsyn motors. These motors have the property that if two of. them are wired together in an A. C. circuit and the rotor of one is turned through a given angle, the rotor of the second will turn through a like angle. The Selsyn motors 43 (Figure 8) and 49 (Figure 6) are to bear such a relationship to each other. One wire of the motor 43 is grounded but the other runs to the contact brush 44 carried by the housing and making contact with the circular arc 44a. The are 44a is insulated from the other arcs by the insulation at 45 in Figure 10. A conductor 445 runs from the arc to the segment of the track 3 where a brush 495 .(see Fig. 6), conducts the current by means of conductor 49a to the Selsyn motor 49. Hence if the rotor of 43 be set at a certain angle the rotor of the motor 49 will take a like angle when the two motors are in circuit through the track and arc segments. Each segment of track is insulated from the other. Thus to each segment of arc 44a there corresponds a segment of track 3. On each segment of are there is a Selsyn motor 43 with a certain rotorsetting. On the corresponding segment of track the Selsyn motor 49 must take up the same rotor setting.

The variationinthe,attitude of the rotor of the motor 43 is regulated from a given initial setting by the magnitude of the windvelocity. The revolutions of the windmill 45 are determinedbythe wind speed. The windmill 'driyesthe gears 46 and 46a and shaft 460 which rotates the ballsAT.

As the rate of rotatiton-increases the balls fly,out ward and raise the square shaft 46d and arms 48. Connecting rods 48a connect the arms 48 with a crank on the motor shaft. The connecting rods have right and left-hand threads at their ends so that the armatures may be given a predetermined setting at any predetermined wind velocity. If

the wind velocity is difierent fromthis value, the vertical position of the arms 48 will change.

Only the motors lying on the windward and lee ward sides are connected to the arm 48. The motors on the other two sides have the attitudes'of' their rotors fixed by a connecting rod 4811 run ning to the housing. (See Fig. 9.)

wings take up either 0 or 90 attitudes with respect to the track, the 0 attitude being on the track side where the wings are advancing into the wind. These attitudes are maintained regardless of the wind velocity.

Each motor in the housing makes contact with a segment or are of the circular conductor 4411. (See Figure 9.) Each arc is insulated from the neighboring one. As the wind changes in direction the housing is rotated. If the rotation is large enough one motor with a certain rotor setting passes oil a segment of 44a and a new motor with a new setting comes on to the arc. The result is a change in the rotor setting in the wing Selsyn motor.

Let the circuit from one of the Selsyn motors 43 lead to the Selsyn motor 49 in the wing. '(See Figures 6, 8, 10, 11, and 12.) The Selsyn motor shaft carries the arm 59. Just below is another arm 53 carried by the gear 51 which meshes with another gear 52 on the shaft 34a. The gears are of the same diameter sothat the angular changes of shaft and arm 53 are alike. When the Selsyn motor moves the arm 50, this arm makes contact with one of two spring electrical contacts 54, and 55 carried on the lower arm 53. circuit for the motor 38 passes through the contact and arm 50. The wing is then rotated by the worm 39 and gear 40. If electrical contact had been made with the other contact, the motor 38 would have run in the opposite direction. Thus the angular attitudeof the wing is controlled by the wind vane.

Since the wing takes up both plus and minus angles 0 (see Fig. 1) with respect to the track it should have an airfoilsection of zero mean camber. An investigation of wings possessing airfoil sections of zero camber shows that the specific value (In /CD may be improved by hinging the aft portion of the wing and rotating it through an appreciable angle. For instance, a 10 flap angle greatly improves the specific value for the M-6 airfoil. Accordingly the wings (Figures 6, 13 and 14) have a hinged flap 56. As the angular attitude of the wing changes from plus to minus referred to the track, the flap angle likewise changes from plus to minus. This procedure keeps the convex side of the mean camber line always toward the direction of progression.

The change in flap position may be made to depend on the attitude of the wing. The'iiap 56 has the spar 57 within extending over the span. (See Figures 13 and 14.) Hinges 58 and a'bracket 59 serve to support the flap on the main wing structural member 34a. The flap carries the horn 59. A link 60 connects the horn with a bell crank 61. Another arm of the bell crank is con nected to the connecting rod 63. At the opposite end of this rod a universal joint 64 connects the 7 rod to a threaded rod 65 which runs through the That is, on the sides of the track parallel to the wind, the- The electrical when the. connecting rod has travelled a given" distance ineither direction. This distance will correspond to theangular position predetermined for the flap.

,The reversal of the motor is accomplished by-the device shown in Figure 13. A passage 73 extends through the wing. 'Near. the center of the passage is a ball '74 with a supporting rod 75 leading tothe main wing structure where it is hinged at 76. Thedirection of the flow through the passage determines which way the flap will be moved. if the flow is up through'the passage, as in Figure .13, the rod will make contact with the electrical contact 77-and resultin the motor turning in such a direction that the trailing edge of the fiap- 56 comes down. When the flow through 73 reverses the motor will be reversed and the flap angle also.

-'The wings may carry end shields 79 at the wing tips, as in Figures 3, ,15 and 16. This end shield will be most, efficient in reducing the induced drag when the wing height tochord ratio (thatis, the geometric aspect ratio) is small. .In any :case, an improvement is obtained if the boundary layer on the end shield is accelerated.

The boundary layer consists of the air close to the surface which has been retarded by friction with thawing surface. The boundary layer may be acceleratedby blowing out the slot 80. This is accomplished by the electric motor 81 and conventional fan- 82 into the disk interior 84 and thence out the slot I. v

. The interior of the shield is divided into two compartments 84 and 85 and the fan 82 draws its air from the rear compartment 85 through the opening in the shield. In this case the boundary layer is drawn into the shield by the addition of kinetic energy andrthe operation serves to improve the effectiveness of the shield. This prin'- ciple is well known inaerodynamics and the term power plant." The energy derived from the translation ofthe-wings may also be used to perform other useful work besides the rotation of the generator shaf t.

It should be understood that I do not limit myself to the disposition of wings shown in Figure 2. In particular, where I use a few wings, so that the path speed is larger than the wind speed I orient both the advancing and retreating win s substantially along the path.

A body is called broad if it has a relatively large extension transverse to the direction of flow of fiuidp'ast it.

While the form of this apparatus herein describedconstitutes a preferred embodiment of the inventiomit is to be understood that the in- The exit 83 of the fan leads vention is not limited to these exact forms or to a path, a group of wings pivotally mounted on the prime mover only since by simply reversing the process the fluid-rotor may receive power to motivate the fluid. That is, changes may bemade without departing from the scope of the invention which is defined in the appended claims.

I claim:

1. A plurality of wings following each other substantially parallel to themselves about a closed path associated with a flow of fluid, an element rotated by the relative flow, a device sensitive to the flow direction, and means to coordinate the inertia force of the rotating element with the direction sensitive device to create automatically and surely a desired set of lifting conditions on the wings when they are at particular localities along their path said conditions having as one feature an increase of path speed with an increase in flow speed.

2. A plurality of wings travelling along a noncircular path associated with a flow of fluid, a device sensitive to the flow direction, a speed sensitive device, means to correlate the devices to maintain a given angular relation between the path and the wing along a major portion of the windward path.

3. A plurality of wings following each other substantially parallel to themselves about a closed path associated with a flow of fluid, an

element rotated by the flow, and means to use the inertia force of the element to adjust the attitude and increase the path speed of the wings with an increase of flow speed.

i. A plurality of wings of airfoil section following each other substantially parallel to themselves in succession about a closed path associated with a flow of fluid; and a device sensitive to the intensity of the flow cooperating with direction sensitive means to alter the angle 0 of a wing relative to the portion of the: path substantially transverse to the flow according to the following equations when either or both terms of the equation for 0 are varied by as much as either plus or minus fifty per cent:

CDPHA DP V am es 6 V 31R,

leaves TM cooperating with a speed sensitive device to maintain the angle between the wing and the path along a major portion of the path transverse to the direction of flow. 1

6. A plurality of wings travelling about a closed path associated with a flow of fluid, and a means to assign a desired angle to a wing automatically in accordance with the flow velocity and direction, said means being independent of the translation of the blades along the path.

. 7. A wind actuated prime mover comprising a path, a device sensitive to the wind direction and an airscrew cooperating to alter the angular attitude of the wings along a specified section of the path in accordance with the direction and intensity of the wind.

8. A wind actuated prime mover comprising a path, a group of wings pivotally mounted on the path, a device sensitive to the wind direction cooperating with a device sensitive to the wind velocity to give such a specific angular attitude of the wings to the path at specific path localities in accordance with the direction and intensity of the wind that the path speed increases when the wind speed increases.

9. A wind actuated prime mover comprising a plurality of wings constrained to travel substantially parallel to themselves along a path, a device sensitive to the wind direction, an element rotated by the wind; and means to coordinate through a Selsyn motor the speed sensitive device and the inertia force of the rotating element so as to control the angular attitude of a wing on a definite segment of the path inaccordance with the wind velocity and direction.

10. In a wind actuated prime mover compris ing a non-circular path, wings pivotally mounted on the path to travel along it, a device sensitive to the wind direction cooperating with a speed sensitive device to maintain a given angular relation between the path and the wing along the major portion of the windward path.

11. A wind actuated prime mover comprising a track associated with a flow of fluid, a group of wings pivotally mounted on the track, a speed sensitive device cooperating with a device sensitive to the wind direction to maintain over a major portion of the track transverse to the wind the angle 0 at a value specified by the following equations when either or both terms of 0 are varied by as much as either plus or minus fifty per cent:

12'. A plurality of wings rotatable about an axis and provided with hinged spanwise flaps, and means to move the flaps relative to the wing proper, said means functioning in accordance with the pressure on the forward portion of the wing.

13. A plurality of wings rotatable about an axis and provided with hinged trailing edge flaps, and means to move the flaps relative to the wing proper with power from the relative air flow, said means functioning automatically in accordance with the angular relation of the wings to the relative wind.

14. A plurality of Wings rotatable about a parallel axis and provided with hinged trailing edge flaps, means to move the flaps relative to the wing proper with power derived from the relative air flow, said means functioning automatically in accordance with the angular relation of the wings to the relative wind. 150

15. In combination with a body associated with a flow of fluid and capable of experiencing a force transverse to the direction of flow, an end shield having an opening in its surface for boundary layer energization and means to cause a flow through the opening.

16. In combination with a broad body associated with a flow of fluid and capable of experiencing a reduction of pressure transverse to the direction of flow, an end shield having an opening in its surface for boundary layer energization and means to cause a flow through the opening.

17. A wind actuated prime mover comprising a track, a group of wings pivotally mounted on the track, and shields at the ends of the wings having openings in their surface and means to cause a flow therethrough.

18. A wind actuated prime mover comprising a track, a group of wings pivotaliy mounted on the track, and shields at the ends of the wings having openings in their surface for energization of the boundary layer and means to cause a flow therethrough dependent on the relative wind.

19. A wind actuated prime mover comprising a lower track, a group of wings pivotally mounted on the track and constrained to the track against upward thrusts, an upper track in part supported by the wings to take the side thrust of the wings, and means to use the wings to do useful work.

20. A wind actuated mover comprising a track, a group of wings pivotally mounted thereon and constrained thereto against upward thrusts, and an upper track in part supported by the wings to take the side thrust.

EDWARD A. STALKER. 

